What is the value of c so that y=x^2+9x+c is a perfect square trinomial?

Question

A. 18
B. 9/2
C. 9/4*
D. 81/4
Check my answer please I think it's C.

Answer 1

x^2 + 9 x +c = y
complete the square
x^2 + 9 x = y -c
x^2 + 9 x + (9/2)^2 = y -c + (9/2)^2
well, that is
on the left there

x^2 + 9 x + (81/4)

which is the same as
(x+9/2)^2

lo and behold, look at D.

Answer 2

thanks so much both of yall!

Answer 3

fyi if you couldn't understand what damon meant it's

D

👍🏻

Answer 4

D. 81/4